Todays Project - What did you do today?

[f350ca]

Been handling too much wood, my hands are clean, and it was too hot today to be working outside so we ventured back into the lonely machine shop.
The 3 jaw for the hardinge was badly bell mouthed so thought we'd tune it up. Tore it apart to clean the scroll and found the back side with the pinions totally dry, not a hint that it ever had lube, HUM. There was a small ding on the end of the mouth that was affecting the fit when I checked with blueing. The other day I repaired that with a bit of scrapping to get a good contact impression.
Set up the tool post grinder and dressed a wheel, which is for a valve seat grinder, have a bunch of them in different sizes, 9/16 course thread bore.


Dave from one of the other forums leant me a set of spacers he'd made to preload the jaws.



After grinding I have between .0005 and .0015 runout, on different sized stock. Not repeatable, clamp the pin and one time you'll get .0005 the next time .0015, pretty much the nature of a 3 jaw, but the dowel pin stays parallel to the bed within .00025 as interpolated off a 1/2 thou test indicator 2 1/2 inches from the chuck.



NOW THE INTERESTING PART.
I've read you should use the pinion marked 0 to get the best results. I do but to be honest have never noticed any difference. I tightened the chuck on the spacers using the 0 one before I ground the jaws. Now if I use the other pinions I get 4 to 5 thou runout on the test pin, never better than 3 and the test pin will be a thou or worse off parallel. Go back to the 0 pinion and all is well. Tomorrows project is to check the 12 inch Bison chuck on the Summit and see if it gives similar results.